全文获取类型
收费全文 | 4109篇 |
免费 | 276篇 |
国内免费 | 400篇 |
专业分类
化学 | 561篇 |
晶体学 | 19篇 |
力学 | 331篇 |
综合类 | 77篇 |
数学 | 2827篇 |
物理学 | 970篇 |
出版年
2024年 | 8篇 |
2023年 | 52篇 |
2022年 | 57篇 |
2021年 | 66篇 |
2020年 | 72篇 |
2019年 | 113篇 |
2018年 | 114篇 |
2017年 | 130篇 |
2016年 | 129篇 |
2015年 | 102篇 |
2014年 | 207篇 |
2013年 | 337篇 |
2012年 | 159篇 |
2011年 | 224篇 |
2010年 | 237篇 |
2009年 | 257篇 |
2008年 | 260篇 |
2007年 | 243篇 |
2006年 | 235篇 |
2005年 | 213篇 |
2004年 | 193篇 |
2003年 | 139篇 |
2002年 | 174篇 |
2001年 | 124篇 |
2000年 | 110篇 |
1999年 | 105篇 |
1998年 | 86篇 |
1997年 | 86篇 |
1996年 | 61篇 |
1995年 | 66篇 |
1994年 | 45篇 |
1993年 | 29篇 |
1992年 | 41篇 |
1991年 | 19篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 33篇 |
1980年 | 28篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1973年 | 8篇 |
排序方式: 共有4785条查询结果,搜索用时 31 毫秒
11.
Yao Ping HOU 《数学学报(英文版)》2005,21(4):955-960
A signed graph is a graph with a sign attached to each edge. This paper extends some fundamental concepts of the Laplacian matrices from graphs to signed graphs. In particular, the relationships between the least Laplacian eigenvalue and the unbalancedness of a signed graph are investigated. 相似文献
12.
Matrix extensions and eigenvalue completions, the generic case 总被引:2,自引:0,他引:2
William Helton Joachim Rosenthal Xiaochang Wang 《Transactions of the American Mathematical Society》1997,349(8):3401-3408
In this paper we provide new necessary and sufficient conditions for the so-called eigenvalue completion problem.
13.
本文给出了一个判定最大无关组的充要性定理及其证明.同时对用矩阵的行变换求最大无关组这一问题进行了点滴分析并介绍了一个解齐次线性方程组的简便方法。 相似文献
14.
In this paper, we provide numerical means to compute the quasi-stationary (QS) distributions inM/GI/1/K queues with state-dependent arrivals andGI/M/1/K queues with state-dependent services. These queues are described as finite quasi-birth-death processes by approximating the general distributions in terms of phase-type distributions. Then, we reduce the problem of obtaining the QS distribution to determining the Perron-Frobenius eigenvalue of some Hessenberg matrix. Based on these arguments, we develop a numerical algorithm to compute the QS distributions. The doubly-limiting conditional distribution is also obtained by following this approach. Since the results obtained are free of phase-type representations, they are applicable for general distributions. Finally, numerical examples are given to demonstrate the power of our method. 相似文献
15.
Mixed and hybrid finite element methods for the resolution of a wide range of linear and nonlinear boundary value problems (linear elasticity, Stokes problem, Navier–Stokes equations, Boussinesq equations, etc.) have known a great development in the last few years. These methods allow simultaneous computation of the original variable and its gradient, both of them being equally accurate. Moreover, they have local conservation properties (conservation of the mass and the momentum) as in the finite volume methods.The purpose of this paper is to give a review on some mixed finite elements developed recently for the resolution of Stokes and Navier–Stokes equations, and the linear elasticity problem. Further developments for a quasi-Newtonian flow obeying the power law are presented. 相似文献
16.
利用Ditzian-Totik光滑模,研究了推广的Kantorovich算子在Ba空间中的逼近,得到逼近的正定理与等价定理.所得结果改进、推广和统一了一些作者的结果. 相似文献
17.
María G. Armentano Ricardo G. Durn 《Numerical Methods for Partial Differential Equations》2003,19(5):653-664
In this article we analyze the effect of mass‐lumping in the linear triangular finite element approximation of second‐order elliptic eigenvalue problems. We prove that the eigenvalue obtained by using mass‐lumping is always below the one obtained with exact integration. For singular eigenfunctions, as those arising in non convex polygons, we prove that the eigenvalue obtained with mass‐lumping is above the exact eigenvalue when the mesh size is small enough. So, we conclude that the use of mass‐lumping is convenient in the singular case. When the eigenfunction is smooth several numerical experiments suggest that the eigenvalue computed with mass‐lumping is below the exact one if the mesh is not too coarse. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 653–664, 2003 相似文献
18.
Let Um be an m×m Haar unitary matrix and U[m,n] be its n×n truncation. In this paper the large deviation is proven for the empirical eigenvalue density of U[m,n] as m/n→λ and n→∞. The rate function and the limit distribution are given explicitly. U[m,n] is the random matrix model of quq, where u is a Haar unitary in a finite von Neumann algebra, q is a certain projection and they are free. The limit distribution coincides with the Brown measure of the operator quq. 相似文献
19.
It has been observed that a quantum theory need not be Hermitian to have a real spectrum. We study the non-Hermitian relativistic quantum theories for many complex potentials, and obtain the real relativistic energy eigenvalues and corresponding eigenfunctions of a Dirac-charged particle in complex statically and spherically symmetric potentials. Complex Dirac–Eckart, complex Dirac–Rosen–Morse II, complex Dirac–Scarf and complex Dirac–Poschl–Teller potential are investigated. 相似文献
20.